It is known to produce high-molecular weight polyureas from di- or polyisocyanates or the so-called isocyanate pre-polymers and diamines or polyamines by polyisocyanate polyaddition. It has been attempted to produce these polyureas in the form of fine powders. All methods of producing such powders, however, require the use of auxiliary liquids. For example, an isocyanate prepolymer may be used in organic solvents or the amine may be used in aqueous solution. The powder is always obtained first as a dispersion or suspension in the liquid and must be subsequently isolated and dried.